The present invention generally relates to packaging and more particularly to a method and apparatus for making unitary packages holding a plurality of components with each package containing a load that has a covering of a web of material wrapped around it.
Case packing or boxing is a common way of shipping multiple unit products. The multiple unit products are generally stacked in a corrugated box or are wrapped with kraft paper with the ends of the kraft paper being glued or taped. Another way of shipping such products is by putting a sleeve or covering of heat shrinkable film around the products and shrinking it to form a unitized package. The use of heat shrinkable film is described in U.S. Pat. Nos. 3,793,798; 3,626,654; 3,590,509 and 3,514,920. A discussion of this art is set forth in U.S. Pat. No. 3,867,806.
The present invention provides a simple more reliable and cheaper method of unitizing multiple unit products into a unitary package.
When the present process and apparatus is compared with other apparatus and processes currently used to pack products in corrugated boxes and the cost of the corrugated boxes themselves, the invention shows an enormous cost savings. The invention has comparable costs with kraft wrap but it gives a much tighter and better unitized package than that possible with kraft wrap. In addition to these factors the invention has a product visibility which is not present in boxes and kraft wrap. When the invention is compared with most existing shrink film systems the proposed system offers packaging speed, reliability of package seal and energy savings in that less energy is required to package the products.
A basic problem with shrink packaging is that the primary strength and reliability of the package is determined by the consistent quality of the seals. These seals depend on a careful maintenance of the sealing jaw and are never as strong as the film itself. The time that it takes to make the seals is a limiting factor on the possible speeds of most shrink systems.
The present invention may or may not require a structural seal depending upon the film type which is used with the invention. The invention is designed to function with either film types such as P.V.C. that have sufficient tack not to require heat sealing or with film types such as polyethylene that require heat sealing. In the present invention the system provides for a sealing mechanism which effectively seals the outer layer of film to the layer under it simultaneously as the trailing edge of the film is severed from the load. Thus the time limitation to make the seal occurs with the severing of the packaged load so that the packaging speed is unaffected.
The use of wrapping machinery in the art is known and one such apparatus is shown by U.S. Pat. No. 3,003,297 in which tape is placed by a rotating ring on a box carried by a conveyor line. A complex cutting and holding mechanism is used to place the tape on each box and cut it off with the process being repeated for each box. The use of the adhesive on the tape to bond it to the package is an integral part of the function of this concept. Without this adhesion it would not work either in single, multiple or spiral configurations. The unique design and function of the clamps in the present invention do not require a bonding of the film to the product in order for the system to operate.
U.S. Patent No. 2,088,133 discloses a reverse wrapping wire tying machine. In the reference a gripper mechanism holds the band in position with respect to the load to be wrapped and a rotatable ring drive rotates the band around the load until the band has completed more than one wrap of the load and passes over the body of the gripper. A separator slide is used to separate the leading edge of the band from the underlying band and a second gripper mechanism attaches to the separated band. A heat sealing mechanism welds the wrapped layer band to the band underneath it and a cutting mechanism severs the leading edge of the band held by the second gripper mechanism which then becomes the trailing edge of the succeeding wrap. When the band is severed the ring drive mechanism is rotated in a reverse direction on another load with the various gripping and cutting mechanisms functioning in the same manner.
The significant improvements of this invention over reference '133 are; its ability to wrap multiple layers, its ability to handle stretch film, its ability to spiral wrap, and its extremely simplified operation and construction. It should be noted that '133 requires eleven separate complex mechanisms and ten operations to accomplish a clamping function that the present invention does with four simple mechanisms and four operations.
Other references of interest which are pertinent to rotatable drives for wrapping packages are disclosed in U.S. Pat. Nos. 3,820,451, 3,331,312, 3,324,789, 3,309,839, 3,207,060, 2,743,562, 2,630,751, 2,330,629, 2,054,603 and 2,124,770. A similar reference of interest is U.S. Pat. No. 2,982,065.
Another application in packaging is shown by U.S. Pat. No. 3,514,920 in which heat shrink film is wrapped around a pallet supporting a plurality of cartons. Furthermore, it is also known in the art to spirally wrap articles. Such spiral wrapping is shown in U.S. Pat. Nos. 3,778,199, 3,549,077, 3,191,289 and 2,716,315.
The present invention uses stretchable plastic film in its preferred embodiment since the mechanical stretching of the film utilizes its strength better than a heat shrink wrap. The elasticity in the film holds the products under more tension than either the shrink wrap or the kraft wrap particularly with products which settle or relax when packaged.
Various apparatus and processes have been developed by the present inventors to utilize stretch material in package wrapping. Such apparatus and processes are disclosed in U.S. Pat. No. 3,867,806 and U.S. patent applications Nos. 454,477, 478,523 now abandoned and 568,269 now U.S. Pat. No. 4,050,220 which have been filed by the present named inventors of this invention. These applications are incorporated herein in their entirety in this application by reference.
Additional benefits occur in the present invention over the prior art in that no changeover is required in handling random size units of a variety of materials as the apparatus is constructed to handle such random size units. Furthermore, the apparatus provides a substantially continuous wrapping operation so that loads can be wrapped at any desired speed and for any time period since the invention can be equipped with an automatic roll changing mechanism. A significant economic factor is also present in the present invention as the power requirements are significantly less than those of shrink systems since there is no heat tunnel required and greater speeds of operation are possible because of the elimination of the conventional heat seal which is used in shrink type wrapping. However, the invention can be used to place shrink film on a load that is then run through a shrink tunnel. Because of the simplicity of the construction of the invention there is a greater stability of the wrapping apparatus with low maintenance being required to maintain the apparatus and a corresponding reduction in breakdown time. Another desired characteristic resulting from the apparatus construction is that the invention can be operated in any plane thus allowing it to be used in various space saving positions.